INSTINCT. 
—I mean Aphides and Locusts,—are the best 
examples of this order. 
4 much as the world has suffered from 
_ these animals, it is extraordinary that so few 
_ observations have been made upon their history, 
_ economy, and mode of proceeding. 
_ The egys of the locusts were no sooner 
: hatched in June,” says Dr. Shaw, “ than each 
_ of the broods collected itself into a compact 
body, of a furlong or more in square, and then 
_ marching directly forwards towards the sea, they 
_ let nothing escape them; they kept their ranks 
| _ dike men of war, climbing over as they advanced 
_ every tree or wall that was in their way; nay, 
| ‘they entered into our very houses and bed- 
_ chambers like so many thieves. A day or two 
i after one of these hordes was in motion, others 
_ were already hatched to march and glean after 
2 - Having lived near a month in this 
_ manner they arrived at their full growth, and 
threw off their nympha state by casting their 
outward skin.” “ The transformation was per- 
formed in seven or eight minutes, after which 
they lay for a short time in a torpid and seem- 
ingly languishing condition ; but as soon as the 
sun and the air had hardened their wings by dry- 
ing up the moisture that remained on them after 
casting their sloughs, they re-assumed their 
former voracity with an addition of strength 
and agility.” 
“ According to Jackson they have a govern- 
ment amongst themselves similar to that of the 
bees and ants; and when the king of the locusts 
rises, the whole body follow him, not one soli- 
fary straggler bemg left behind. But that 
locusts have leaders like the bees or ants, dis- 
tinguished from the rest by the size and splen- 
dour of their wings, is a circumstance that has 
not yet been established by any satisfactory 
evidence; indeed, very strong reasons may be 
urged against it.” 
“ The last order of imperfect associations 
_ approaches nearer to perfect societies, and is 
that of those insects which the social principle 
_ urges to unite in some common work for the 
benefit of the community. 
“ Many larve of Lepidoptera associate 
_ with this view, some of which are social only 
_ during part of their existence, and others during 
the whole of it. 
“ A still more singular and pleasing spectacle 
when their regiments march out to forage, is 
exhibited by the Processionary Bombyx. This 
moth, which is a native of France and has not 
yet been found in this country, inhabits the 
vak. Each family consists of from 600 to 800 
individuals. When young, they have no fixed 
habitation, but encamp sometimes in one place 
and sometimes in another under the shelter of 
_ their web; but when they have attained two- 
thirds of their growth, they weave for themselves 
acommon tent. About sun-set the regiment 
leaves its quarters; or, to make the metaphor 
harmonize with the trivial name of the animal, 
the monks their cenobium. At their head is a 
chief, by whose movements their procession is 
regulated. When he stops all stop, and pro- 
ceed when he proceeds; three or four of his 
immediate followers succeed in the same line, 
VOL. IIT. 
17 
the head of the second touching the tail of the 
first; then comes an equal series of pairs, next 
of threes, and so on as far as fifteen or twenty. 
The whole procession moves regularly on with 
an even pace, each file treading on the steps of 
those that precede it. If the leader, arnving 
at a particular point, pursues a different direc- 
tion, all march to that point before they turn.”* 
Examples of occasional associations, more 
or less resembling all these, and of which the 
object is in many instances still obscure, may 
be found in all the classes of the higher ani- 
mals, as is obvious, when we consider to how 
many tribes of animals the term gregarious is 
usually applied, e. g. to almost all the Rumi- 
nantia, some of the Pachydermata, and a few of 
the Rodentia. Some of the genus Muride (rats 
and mice) have been long known to migrate, 
occasionally, in a manner resembling the 
locusts. ‘ The general residence of the lem- 
ming,” says Pallas, “is in the mountainous 
parts of Lapland and Norway, from which 
tracts at uncertain periods it descends in im- 
mense troops, and by its incredible numbers 
becomes a temporary scourge to the country, 
devouring the grain and herbage, and com- 
mitting devastations equal to those of an army 
of locusts.” “It is observable that their chief 
emigrations are made in the autumns of such 
years as are followed by severe winters.” ‘The 
ground over which they have passed appears 
at a distance as if it had been ploughed, the 
grass being devoured to the roots in numerous 
stripes or parallel paths, of one or two spans 
broad, and at the distance of some yards from 
each other.” “ The army moves chiefly at night, 
or early in the morning. No obstacles that 
they meet in their way have any effect in 
altering their route, neither fires, nor deep 
ravines, nor torrents, nor marshes, nor lakes ; 
they proceed obstinately in a straight line, and 
hence many thousands perish in the waters.” 
“ If disturbed, in swimming over a lake, by oars 
or poles, they will not recede, but keep swim- 
ming directly on, and soon get into regular 
order again.” “In their passage over land, if 
attacked by men, they will raise themselves up, 
uttering a kind of barking sound, and fly at 
the legs of their invaders, and will fasten so 
fiercely on the end of a stick, as to suffer them- 
selves to be swung about without quitting their 
hold, and are with great difficulty put to flight.” 
‘“‘ The major part of these hosts is destroyed by 
various enemies, as owls, hawks, weasels, ex- 
clusively of the number that perish in the 
waters, so that but a small part survive to 
return, as they are sometimes observed to do, 
to their native mountains.” The campagnol, 
or short-tailed rat, has been known to com- 
mit similar ravages in France. It is obvious 
here, that under the influence of this instinct, 
and of the excitement of numbers (in which, 
as in our own race, the principle of imitation 
is probably much concerned) the usual motives 
to action of these animals are superseded, and 
their usual habits changed. 
We are still uncertain as to the use, or final 
* Introduction to Entomology, letter xvi. 
c 
